This invention relates in general to vibration damping devices and, in particular, to an improved vibration damper for suspended electrical transmission cables and the like. In a typical suspended cable, Aeolian vibrations are induced in each span as a result of the wind flowing past it. The vibration is caused by vortices which are formed on the leeward side of the cable. These vortices alternate in direction, setting up alternating vertical forces which, in turn, cause the cable to vibrate, largely in a vertical plane. The frequency at which the directions of those vortices alternate is proportional to the wind velocity and inversely proportional to the diameter of the cable. As the wind speed increases, the frequency of alternation of the vortices increases, thereby causing the frequency of the resultant vibrations to increase likewise. The frequency of alternation of these vertical forces applied to the cable is the same as one of the resonance frequencies of that particular span and therefore the cable resonates. A particular span of cable, which is a continuous electrical conductor, suspended between two points, has a large number of resonance frequencies. The resonance frequencies of a particular cable span depend upon the weight per unit length of the cable, the span length, and the tension in the cable. They also depend upon the gravitational constant. The vibration pattern of the line takes the form of a sinusoidal deflection curve with the vibration originating in the span and traveling back and forth along the length of the span. Nodes are established at the ends of the span and, usually, both loops and nodes between the ends.
As the cable vibrates, it flexes at the points at which it is clamped and also undergoes significantly large values of dynamic mechanical stress. Such repeated flexing and great stress lead to fatigue failure in the cable and damage to suspension hardware. This vibration is substantially reduced over a wider range of wind speeds at both ends of a span as well as elsewhere in the span by means of a damper employing this invention installed at only one end of the span.